We have isolated a chymotrypsin-like and a trypsin-like proteinase from human dermis; these enzymes are probably of mast cell origin. We will: 1. Refine purification methods and further characterize the physical, chemical and kinetic properties of these enzymes. 2. Produce antibodies to these enzymes and use them for radioimmunoassays and immunocytological investigations. 3. Localize these proteinases in tissue at the light and ultrastructural level and determine their relationship to mast cells. 4. Prepare enriched mast cell populations and investigate whether the enzymes are secreted along with other mast cell mediators. We will also determine whether these enzymes are secreted by mast cells in vivo. 5. Investigate the proteins cleaved by the chymotrypsin-like proteinase in basement membrane which will probe the nature of basement membrane. 6. Study the role of the chymotrypsin-like proteinase disease in cutaneous disease with special attention to cutaneous mast cell disease and bullous pemphigoid. We have demonstrated that psoriatic epidermis has increased levels of plasminogen activator and that levels of the enzyme correlate with disease activity. We will: 1. Characterize the mechanism for increases in plasminogen activator activity in psoriasis which involves determining whether there is increased synthesis of plasminogen activator enzyme, increased activation of plasminogen activator zymogen, or decreased in plasminogen activator inhibitor in psoriasis. 2. Explore the effects of plasminogen activator on epidermal cell replication. 3. Investigate whether plasminogen activator or plasmin is the active principle which attracts polymorphonuclear leukocytes to the psoriatic epidermis. We will also study whether proteinases play a role in polymorph accumulation in epidermal injury from toxins. We have identified a thiol proteinase, operative at neutral pH, in epithelium. This proteinase is capable of degrading epidermal cell surface proteins. We will purify and characterize this proteinase and determine its role in epidermal physiology.